1. Field of the Invention
The present invention relates to a method of forming a field oxide film in a semiconductor device, and particularly, to a method of forming a field oxide film of semiconductor device which can increase an active region by removing a bird's beak produced by a selective thermal oxidization process.
2. Information Disclosure Statement
In general, a field oxide film is formed to isolate semiconductor devices from each other. A prior art method of forming a field oxide film is described below with reference to FIG. 1.
A field oxide film 4 composed of a thermal oxide film is formed by sequentially forming a pad oxide film 2 and a nitride film 3 on a silicon substrate 1, thereafter etching a selected part of the pad oxide film 2 and the nitride film 3, and thereafter performing a thermal oxidization process. The prior art technology has a disadvantage in that the active region is decreased by the occurence of a bird's beak "A" as the thermal oxide film penetrates below the nitride film 3.